DETROIT — In a seven-game series in which every game could have gone either way, the Detroit Red Wings battled back from a 3-0 deficit before falling just short against the San Jose Sharks.

It shows how little separated the teams. The Red Wings are that close.

But the Sharks have beaten them two years in a row in the second round of the playoffs, a clear indication that something is missing.

As the Red Wings head into the offseason, changes are inevitable. The defense needs retooling, either through free agency or a trade. If Nicklas Lidstrom retires, they will need to make a significant move. If the captain comes back, a slight roster tweak should be good enough to make the Red Wings Stanley Cup contenders again.

“The league is really, really close,” general manager Ken Holland said after Thursday’s 3-2 loss in Game 7. “We got to make some moves, but we got the nucleus of a good team.

“We got a lot of good players, we’ll see how we can tweak it. We got to figure out a way to get on the other side of this. Find a way to win by one instead of lose by one.”

The age issue with this team always gets overblown. They have a lot of older players, but they also have a strong nucleus of forwards in their prime. Scoring should not be a problem.

Pavel Datsyuk and Henrik Zetterberg were outstanding in the playoffs, reaffirming their status as two of the best two-way players in the NHL. They have a good supporting cast of skilled players in Johan Franzen, Danny Cleary and Valtteri Filppula. Aging veterans Todd Bertuzzi and Tomas Holmstrom still have another effective year in them.

The club also has experienced good growth from its third- and fourth-line players. If they re-sign unrestricted free agents Patrick Eaves and Drew Miller, who might be able to get better deals elsewhere, the Red Wings will maintain a strong and young core of grinders that includes Darren Helm and Justin Abdelkader. These players bring speed, physical play and even some offense.

Speedy Jan Mursak will be added to the mix next season, and possibly Cory Emmerton, too.

The Red Wings will have a tough decision on whether to re-sign longtime role player and team leader Kris Draper, who turns 40 in 10 days but wants to continue playing. Future Hall of Famer Mike Modano will retire. If that wasn’t clear before the playoffs, it was evident after he was scratched in nine of 11 games.

There will be a couple of changes on defense. Lidstrom likely won’t be one of them. He might win his seventh Norris Trophy as the league’s top defenseman next month and surely realizes himself that he is too good to walk away. Expect him to re-sign for the same $6.2 million he earned this season (he’s not going to take less than Brian Rafalski’s $6 million).

“I truly believe the core group we have, looking at the top players, Zetterberg and Datsyuk, and you have guys behind them — Franzen, Filppula, Kronwall, Stewie — you got guys that are making strides and guys that are star players in this league,” Lidstrom said.

Rafalski, Brad Stuart and Niklas Kronwall, who really stepped up in the playoffs, all have one year remaining on their deals, giving the team a strong nucleus.

Jonathan Ericsson and Ruslan Salei could be gone.

The 6-foot-4, 220-pound Ericsson turned down a multiyear offer worth $2 million a season. He improved this season but hasn’t been nearly as effective as he was during his breakout performance in the 2009 playoffs.

Salei basically was a one-year veteran stop-gap while young Jakub Kindl adjusted to the NHL.

Top prospect Brendan Smith will be given a good opportunity to earn a spot in training camp but might need another half or full season of development with the Grand Rapids Griffins.

The Red Wings’ biggest need is a top-four defenseman.

Forget about Shea Weber. He’s going to re-sign with Nashville, in all likelihood. In any event, the Red Wings don’t make offers to restricted free agents. And if he doesn’t sign with the Predators, the Red Wings would be more apt to pursue him in 2012 when he’s unrestricted.

Perhaps they’ll try to acquire Zach Bogosian of Atlanta, but only through a trade, not an RFA offer sheet. They talked internally about that possibility prior to the trade deadline but apparently decided it wasn’t worth breaking up the core of a Cup contending team.

If the Red Wings move a forward, Jiri Hudler is the most likely candidate. He struggled after returning from a one-year stint in Russia. But his poor season and $2.875 million contract would make him tough to deal unless the Red Wings take another team’s baggage in return.

Would the Red Wings consider moving the enigmatic Filppula? He continues to show flashes of brilliance. He can be a high-level player with his speed, passing and defensive ability. But he is too inconsistent and probably won’t reach that 70-point plateau that seems to be the team’s annual goal for him.

Jimmy Howard stepped up big in the playoffs, cementing his status as the goaltender of the future. He’s a workhorse who will play 60-65 games a season. But who will back him up?

The options include Chris Osgood, who wants to play another season after missing the second half following sports hernia surgery, journeyman Joey MacDonald and perhaps one-time prospect Daniel Larsson. He bolted for Sweden last season but the Red Wings still own his NHL rights.

Thomas McCollum, their top pick in 2008, has struggled in two seasons as a pro and isn’t close to being NHL-ready.

Coach Mike Babcock said earlier this season that this team has a two-year window for winning the Stanley Cup. With a few alterations, the Red Wings can be in the hunt again in 2011-12. Time has not yet passed them by.